grains in lightened pastry cream

Hi chefs! Yesterday i made choux and i filled them with amaretto pastry cream lightened with wipped cream. It was nice. But there is a problem. Whenever i make lightened pastry cream it turns out grainy after it has been stored in the refrigerator for some hours. The same happened when i made a tart with lightened pastry cream and strawberries. The next day it was full of grains. However i never have problem with simple pastry cream. Thanks a lot!

My only thought is that maybe you are over whipping the cream, so the butterfat is solidifying in the fridge? If it was the pastry cream egg clotting it would happen before cooling, and it sounds like your pastry cream skills are fine. how stiff do you whip the cream?

I maybe overwhipping the cream because i cant easily distinguish soft peaks from medium soft peaks. Should cream be folded in pastry cream when it has reached about 35 celsus? And should pastry cream has been whipped to be smooth before cream is added?

soft or medium peaks shouldn't be near over-whipping the cream into butter. I don't remember working with temp when folding whipped c. into pastry c., just waiting for the pastry c. to come down to room temp. At that temp it looks like you are near the butter melting point (look here http://hypertextbook.com/facts/2003/JessicaCheung.shtml) . So I would suggest trying it a bit cooler, but other than that I'm out of suggestions.